Method of creating chemical induced pre-stressed zones in concrete

ABSTRACT

Embodiments of the present invention comprise a method for creating pre-stressed zones in concrete. In one embodiment, a circular blade is coated with a chemical which retards the setting of the concrete. The circular blade is then rolled through the wet concrete, thus transferring the retarding chemical from the blade into the concrete. The region of wet concrete that has the retarding chemical introduced into it does not set until after the surrounding concrete has set and shrunk, thus creating a pre-stressed zone which typically manifests itself as a crack, visible upon setting of the wet concrete. Other embodiments describe alternative ways of introducing the chemical into the wet concrete.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/008,855, entitled “Chemical Induced Pre-Stressed Zones inConcrete,” to Steven L. High, filed on Dec. 9, 2004, which claims thebenefit of the filing of U.S. Provisional Patent Application Ser. No.60/528,687, entitled “Method and Apparatus for Creating Pre-StressedZones in Wet Concrete”, to Steven L. High, filed on Dec. 10, 2003, andthe specifications and claims thereof are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

The present invention relates to a method for creating pre-stressedzones in concrete through the introduction of a chemical while theconcrete is in a liquid stage.

2. Description of Related Art

After a slab of concrete has been poured, one or more pre-stressed zonesare then created in the slab. These pre-stressed zones act to guidecracks along straight and predetermined pathways. Typically, suchpre-stressed zones are created by cutting through an upper portion ofthe concrete with a circular saw that is made to travel in a relativelystraight line across the slab. Use of such a saw, therefore, requiresthat the concrete first be allowed to harden. Hardened concrete is quiteabrasive and thus typically requires a diamond coated cutting blade witha constant flow of water applied thereto. This process is both slow andexpensive. There is thus a present need for a method for installingpre-stressed zones in concrete in a fast and inexpensive manner.

The present invention is directed to a method for creating apre-stressed zone in wet concrete which includes providing wet concrete,providing a chemical capable of retarding, delaying, or inhibiting thesetting of wet concrete, physically penetrating a top surface of the wetconcrete, placing the chemical below the top surface of the wetconcrete, and allowing the wet concrete to set.

In the method, penetrating a top surface can include rolling asubstantially circular blade at least partially through a portion of thewet concrete, as well as pressing a blade at least partially into aportion of wet concrete. The chemical can be sprayed into an opening inthe wet concrete, or the chemical can be sprayed onto a blade that issubsequently placed at least partially into the wet concrete. Thechemical used in the present invention can also be saturated into a ropewhich is then at least partially disposed beneath a surface of theconcrete.

Regardless of how the chemical is added to the wet concrete, after thechemical has been added, the surface of the wet concrete can optionallybe smoothed.

The chemical used in the present invention preferably contains ahydrocarbon solvent and more preferably contains aromatic 100 and/ormineral spirits. Desirable results can also be obtained when sugar-wateris used.

The method of the present invention also includes introducing a chemicalbelow a top surface of wet concrete. This method preferably comprises aroller with a blade that is disposed at least partially around an outersurface of the roller, an axle fixedly or rotatably secured to theroller and substantially axially aligned therewith, one or more handlesfixedly or rotatably connected to the roller, and a chemical applicationsystem which applies a chemical to the blade.

The blade can have a plurality of orifices disposed radiallytherethrough, and through which the chemical is excreted. Or, thechemical can be applied to the blade with a spraying system.

A pump can be coupled to the roller such that when the roller isrotated, a volume of chemical is pumped which is proportional to theamount of rotation experienced by the roller. A plurality of pistons canbe radially disposed within the roller. A cam-shaped member can beattached to an axle thereof such that rotation of the roller causes thecam-shaped member to reciprocate the pistons, thus pumping the chemical.

One or more chemical-distributing wipers can be provided which spreadchemical across the blade. Further, one or more wet concrete scraperscan be provided which help to remove wet concrete that sticks to theblade.

The method can be powered by a mechanism, including but not limited toone or more electric motors, gas motors, pneumatic motors, hydraulicmotors, combinations of these, etc. The power mechanism can be directlycoupled to the method, or a drive mechanism can be provided whichtransfers power from the power mechanism to the roller or the axle. Thepower mechanism can be disposed internal of or external to the roller.

The present invention also relates to a method for introducing achemical below a top surface of wet concrete which includes at least onepropulsion member; a power source having an internal power source, anexternal power source, and/or combinations thereof; a movably positionalblade; and a chemical application system.

The apparatus can also have one or more guide mechanisms. The guidemechanism can be one or more tracks, a string guide, and/or a laserguide.

One or more vibrators can also be provided, and the propulsion membercan include at least one rotatable leg member and/or at least one wheel.The chemical application system can apply a chemical onto a surface ofthe blade, and/or apply the chemical directly into a depression of thewet concrete.

An automated controlling mechanism can be provided, which can optionallyinclude a microcontroller.

The present invention also relates to a method for creating a pre-stresszone in wet concrete which includes providing a rope saturated with achemical, disposing the rope at least partially within wet concrete, andallowing the wet concrete to set. The method can include providing arope holder, and the rope holder can have a spool and/or a spool holder.

Disposing the rope at least partially within the wet concrete caninclude disposing the rope at least partially around a circumference ofa substantially circular rotatable blade. Optionally, after disposingthe rope within the wet concrete, the wet concrete can be smoothed.

The present invention also relates to a method that provides forinserting a chemical-saturated rope below a top surface of wet concretewhich includes a roller, an axle at least substantially axially alignedwith the roller, at least one handle, and a blade circumferentiallydisposed around the roller. The blade can include a channel, a groove,an indentation, or a trough.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises a method for creating a pre-stressedzone in concrete comprising the steps of laying down wet concrete;physically penetrating a top surface of the wet concrete; applying achemical capable of retarding, delaying or inhibiting setting of the wetconcrete at the physical penetration; setting the wet concrete; andcreating the pre-stressed zone in the concrete during or after thesetting of the concrete.

The penetrating step comprises rolling a substantially circular blade atleast partially through a portion of the wet concrete. The penetratingstep further comprises pressing a blade at least partially into aportion of the wet concrete. The applying step comprises disposing thechemical on a blade and placing the blade at least partially into thewet concrete as well as placing a chemical-saturated rope below the topsurface, at least partially within the wet concrete, at least partiallyaround a circumference of a substantially circular rotatable blade. Theapplying step further comprises inserting the chemical into an openingin, and applying the chemical below the top surface of, the wet concretecreated by a blade and then smoothing the wet concrete. The chemicalused can comprise an organic solvent such as aromatic 100, mineralspirits, or a sugar-water solution.

A primary object of the present invention is to negate the arduous task,currently available, for creating pre-stressed zones in set concrete.

Another object of the present invention is to provide a method whichinexpensively enables a user to easily and inexpensively createpre-stressed zones in concrete.

A primary advantage of the present invention is that methods areprovided which enables a user to easily and inexpensively createpre-stressed zones in wet concrete.

Other objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate one or more embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating one or more preferred embodiments of the invention and arenot to be construed as limiting the invention. In the drawings:

FIG. 1 is a top view showing the basic configuration of the apparatus ofthe present invention;

FIG. 2 is a side view showing the blade of the FIG. 1 embodiment havingwiper wheels for evenly distributing the chemical;

FIG. 3 is an exploded perspective view showing the basic construction ofthe roller of the FIG. 1 embodiment;

FIG. 4 is a perspective view showing a motor and drive mechanism mountedoutside the drum of the FIG. 1 embodiment;

FIG. 5 is a perspective view showing an internal drive mechanism removedfrom the drum of the FIG. 1 embodiment;

FIGS. 6A and B are cut-away views showing alternative embodiments of thepresent invention for distributing chemical from the axle to the blade;

FIG. 7 is a perspective view of the 6A and B embodiment in which theblade has been slid away from the axle of the present invention;

FIG. 8A shows an embodiment of the present invention where chemical isinjected into the ports through piston pumps;

FIG. 8B is an alternative view of the embodiment of FIG. 8A wherein thepumps have been removed to more clearly depict this embodiment;

FIG. 9 is a cut-away end view of an embodiment of the present inventionwherein a gear pump is used to supply chemical to the blade;

FIG. 10 shows an alternative embodiment for dispensing chemical into wetconcrete;

FIG. 11A is a side view of an embodiment for placing chemical containingrope into wet concrete;

FIG. 11B is a front view of the blade with a groove for placing chemicalcontaining rope into wet concrete;

FIGS. 12-14 are drawings showing overstressed zones or cracks producedin concrete using the present invention; and

FIG. 15 is a drawing showing the slab of concrete that was used fortesting the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to creating pre-stressed zones orjoints in concrete. More particularly the present invention is directedto creating pre-stressed zones in concrete by introducing a chemicalinto the area where a pre-stressed zone is desired. The chemical delaysthe setting of concrete in this area, thus this portion of the concreteremains wet while the rest of it dries. Since concrete typically shrinkswhen it dries, the shrinkage caused by the rest of the concrete drying,causes pulling away from the still wet portion. This pulling results ina pre-stressed zone being created in this area of the concrete. Afterthe treated portion of concrete finally dries, the pre-stressed zone istypically evidenced by a crack or joint traversing this portion of theconcrete.

The term “chemical” as used throughout the specification and claims isintended to include but not be limited to any chemical, or combinationthereof, which is capable of retarding, delaying, and/or inhibiting thesetting of wet concrete. The chemical used is preferably a common waterand sugar solution, or a commercially available concrete settingretardant such as Sure Lift (J-5), Sure Lift (J-6), Top Etch-Regular orDeep, or a combination thereof. It is also preferable that lubricatingoil be added to the chemical(s) such that any moving parts contacted bythe chemical can be lubricated. The term “rope” as used throughout thespecification and claims is intended to include but not be limited toany type of rope, twine, string, yarn, or structure capable of beingsaturated with a chemical.

The term “concrete” as used throughout the specification and claims isintended to include but not be limited to cements, cement and aggregatemixtures, concrete, mortar as well as any similar mixture or compoundwhich can be poured in a liquid form prior to setting into asubstantially solid form, and for which a retardant, inhibitor, ordelaying agent is known to produce desirable results for retarding,inhibiting and/or delaying its setting into a substantially solid form.

As depicted in FIG. 1, the present invention preferably uses applicatordrum 10 having at least one protruding blade 20 disposed on its surface.Drum 10 is preferably substantially hollow, and is preferably attachedto handle 30 at each end of axle 40. Chemical is applied to blade 20. Asdrum 10 rotates across a section of wet concrete, blade 20 sinks intothe wet concrete and the chemical, disposed on blade 20, is thenintroduced into the wet concrete. Since the concrete is still in aliquid state, the rut caused by blade 20 is filled back in by theinherent liquid flowing capabilities of the wet concrete. If desired, afloat and or screen can be applied to the surface of the concrete wherethe chemical was introduced.

A number of ways of applying chemical to blade 20 can be utilized.Chemical can simply be sprayed onto blade 20. Such spraying can beachieved by a number of apparatuses and can include, but is not limitedto a hand-operated pump sprayer, an electrically powered sprayer, or agas-powered sprayer. As shown in FIG. 2, blade 20 can be sandwichedbetween a pair of wipers 45 such that the chemical applied thereto ismore evenly distributed on the surface of blade 20. While wipers 45depicted in FIG. 2 are in the shape of wheels, numerous otherconfigurations can easily be adapted by those skilled in the art, andwill also produce desirable results. Wipers 45 are preferably made froma plastic, rubber, or a material such as or similar to that known as“Scotch Bright” as manufactured by the 3M Corp. However, any materialcapable of spreading the chemical applied to the blade will producedesirable results.

Since the concrete takes a short duration to flow and close the gapcaused by shoving blade 20 through it, a nozzle can be disposedimmediately behind blade 20 such that chemical emitted from the nozzleis deposited within the gap created by blade 20.

In another embodiment of the present invention, as shown in FIGS. 6A,6B, and 7, blade 20 has ports 70 radially disposed thereabout. Ports 70preferably pass from an inner surface to an outer circumference of blade20. The chemical preferably travels under pressure from an inletdisposed in an interior portion of blade 20 to an exterior circumferencethereof. Pressure used to supply the chemical to blade 20 can begenerated through virtually any manner known such as, but not limitedto, an elevated supply tank, an electric pump, a manual pump, a gaspump, a pressurized gas disposed above the chemical in a sealed tank,etc. In order to provide a flow of the chemical to ports 70, when theirdistal end is positioned substantially beneath drum 10, it is preferablethat the chemical be made to travel through axle 40, which is fixedlyconnected to handle 30. Hollow projection 100 is preferably disposed, ina downwardly projecting manner (determined by user operation),perpendicular to and on axle 40, within an inner circumference of blade20. A frictionally sliding interface is preferably created between adistal end of this projection and an inner circumference of blade 20.Seal 110 is preferably disposed upon the distal end of projection 100,thus reducing or eliminating any leakage of chemical from between thetwo surfaces. While seal 110 can be made from any of the variousmaterials typically used for such applications, seal 110 is preferablymade from “Teflon”, as manufactured by Dupont, or a rubber. In thisembodiment of the present invention, while in operation, the chemicalpreferably passes through an interior portion of axle 40. The chemicalthen travels down projection 100, past seal 110 and through ports 70 ofblade 20 as they come into alignment with projection 100.

FIG. 3 shows an expanded view of the primary components of an embodimentof the present invention. In this embodiment drum 10 comprises twohalves 80 which sandwich blade 20. End-caps 90 are preferably threadedand screw into an external end portion or halves 80. A hole ispreferably disposed through a substantially central portion of end-caps90, through which axle 40 passes from an exterior to an interior portionof drum 10.

Referring now to FIGS. 4 and 5, motor 50 can be disposed in such amanner as to enable drum 10 to be powered. While motor 50 can be poweredby hydraulic, pneumatic, or any other source, motor 50 is preferably anelectrically powered motor. Motor 50 is most preferably a 110 volt ACmotor or a 12 volt DC motor. Motor 50 can, of course, easily be replacedby a small engine which runs off of gas, diesel or another fuel, andthis also produces desirable results. As shown in FIGS. 4 and 5, motor50 can be disposed within drum 10 or external to drum 10. If motor 50 isdisposed exterior to drum 10, a driving chain, belt, shaft, gear, orother mechanism, adaptable for such purposes by those skilled in theart, is preferably provided to cause drum 10 to rotate about axle 40. Ifmotor 50 is disposed within drum 10, a mechanism is preferably providedwhich imparts the rotational energy from motor 50 to drum 10. Suchmechanism can include, and is not limited to, gears as well as belts andpulleys and other commonly known mechanisms. Internally mounted motor 50preferably imparts rotational energy to drum 10 through the aid of africtional interface between an inner surface of drum 10 and motor 50.Motor 50 is preferably secured to axle 40, motor 50 has a rubber drivewheel 60 disposed on its shaft, and drive wheel 60 resides in a mutuallycommunicable manner with an inner surface of drum 10.

The chemical can be applied to blade 20 by piston pumps 120, depicted inFIG. 8A. In this embodiment, piston pumps 120 are disposed at an innerportion of blade 20. The discharge of each pump is preferably connectedto each of ports 70, thus forming a ring of pistons around axle 40. Axle40 preferably has cam 130 disposed thereon. As drum 10 and blade 20rotate about axle 40, cam 130 causes each of pistons 120 to be depressedas they become perpendicularly aligned with the wet concrete, thusinjecting a chemical through their respective ports 70 and into the wetconcrete. FIG. 8B shows a view of axle 40 and blade 20 having pistons120 removed to more clearly show a way in which the chemical can beprovided to pistons 120. In this embodiment, the chemical travelsthrough axle 40, out of port 140 and into chemical chamber 150. Chemicalchamber 150 is preferably formed by plate members 160, rigidly connectedto axle 40, having seals 170 disposed on rim portions thereof. Seals 170are preferably large o-rings and remain in frictional contact with innerside surfaces of blade 20. Thus, as drum 10 and blade 20 rotate aboutaxle 40 and plate members 160, the chemical traveling into chemicalchamber 150 is removed by the pumping action created by pistons 120interacting with cam 130.

In another embodiment, as depicted in FIG. 9, gear pump 180 ispreferably disposed in an inner portion of drum 10. Gear pump 180 ispreferably rigidly connected to axle 40. Gear pump 180 preferably hasroller 190 residing in a mutually communicable manner with it, such thatas roller 190 rotates, gears of gear pump 180 rotate, thus pumping thechemical from axle 40 to ports 70. Roller 190 is preferably frictionallyconnected to an inner surface of drum 10. Since drum 10 rotates aroundaxle 40 and since gear pump 180 is rigidly connected to axle 40, drum 10rotates around gear pump 180. As drum 10 rotates around gear pump 180,roller 190 is caused to rotate due to the frictional interface betweenit and drum 10. Thus, gear pump 180 only operates when drum 10 isrotating. Gear pump 180 is preferably used in conjunction with theembodiment depicted in FIG. 8 where the chemical, after being dischargedfrom pump 180, travels down projection 100, past seal 110 and throughports 70 of blade 20 as they come into alignment with projection 100. Afurther benefit which is realized by incorporating gear pump 180 in theabove-described fashion is that the chemical is only pumped when theinvention is in operation, and the amount pumped is directlyproportional to the distance drum 10 is rotated. Thus, by altering suchthings as the size of gear pump 180, roller 190, and or inner diameterof drum 10, the amount of chemical pumped per distance traveled by theinvention can be adjusted.

In another embodiment, as depicted in FIG. 10, a pneumatic or electricalapparatus 200 is made to traverse the portion of wet concrete to betreated. Apparatus 200 preferably has a retractable blade 210 which iscapable of being inserted into the wet concrete, preferably with avibratory action. Upon removal of blade 210, apparatus preferablyinjects a dosed amount of the chemical into the gap created by blade210. Apparatus 200 then travels a small distance and repeats thisprocess until an entire line of concrete has been treated. In oneembodiment, apparatus 200 operates in an action similar to that of a“frog”. Apparatus 200 preferably drags behind it all hoses and or linesneeded for its operation. Pneumatic motor 220 is preferably connected tolegs 230; thus, when air is supplied to motor 220, legs 230 rotate onerevolution, thus causing the apparatus to take on a “hopping” motion.Numerous manners of guiding apparatus 200 can easily be devised by thoseskilled in the art, however, apparatus 200 is preferably guided throughthe use of foot tracks, string, or a laser.

If foot tracks are employed, they are preferably positioned across theportion of concrete to be treated. They preferably have a channel shapewhich prevents legs 230 wandering out of them. If string is employed,apparatus 200 preferably has guides 240 disposed on an upper portionthereof. String is then passed through guides 240 and each end of thestring is then secured to stakes which have been previously disposedoutside of each end of the portion of the concrete to be treated. Guides240 are preferably elliptically shaped (height diameter greater thanwidth diameter). This prevents apparatus 200 from deviating left orright, but enables it to rise and fall as it traverses the portion to betreated.

In each of the above-described embodiments, the chemical can be appliedto the blade structures in any manner known to those skilled in the art.As such, the chemical can be applied to the blades simply by sprayingthe blades with a common hand-operated spray device. For exampledesirable results can be produced using any of the above-describedembodiments wherein the chemical is applied to the blade by spraying thechemical from a simple squirt bottle or hair-spray type bottle.

Referring now to FIG. 11, in another embodiment, rope 250 is saturatedwith the chemical. Spool 260, containing a roll of rope 250, is thenpreferably disposed on handle 270 of the apparatus. As in previousembodiments, handle 270 is preferably connected to a large, preferablyhollow, drum-like structure 280. Drum 280 preferably has blade 290.Blade 290 preferably has groove 300 disposed about its circumference,within which rope 250 resides. Guide wheel 310 is preferably disposednear an external circumference of blade 290. Guide wheel 310 thusenables rope 250 to properly feed into groove 300. Scraper 320 ispreferably provided to scrape away wet concrete which clings to blade290. Prior to use, a user preferably feeds a portion of rope throughguide wheel 310 and around blade 290. As drum 280 rotates, rope 250 ispulled from spool 260 around blade 290, thus forcing rope 250 into thewet concrete. When the portion of wet concrete has been traversed withthe apparatus, a user simply cuts the rope and the process is repeatedfor the next portion of wet concrete to be treated. Rope 250, withchemical disposed therein and thereon, is left imbedded in the concrete.The chemical preferably diffuses into the portion of wet concreteimmediately surrounding the rope, thus delaying the setting of thisportion of concrete and therefore enabling a pre-stressed zone to becreated therein.

The present invention is not limited to simply creating cracks at rightangles to side portions thereof. Rather the present invention is amethod that can be used to create geometric-shaped cracks in concrete ina manner that will be apparent to as those skilled in the art uponreading this application.

Although more desirable results are obtained by providing a method todispose the chemical into wet concrete, desirable results can beobtained by virtually any manner which enables a chemical to be disposedon top of, or introduced into an area of wet concrete. For example, inan embodiment of the present invention, a user can simply spray a regionof wet concrete using a hand squirt bottle

INDUSTRIAL APPLICABILITY

The invention is further illustrated by the following non-limitingexample.

Example

A slab of concrete having a thickness of six inches was poured. Beforethe concrete set, the rotary-blade apparatus of the present inventionwas used to apply Regular Strength Surface Etch Retarder (containing10%-30% D-Organic Acid), manufactured by Unitex, according to the aboveteachings. The blade in this experiment was set to three differentdepths to compare the results obtained when chemical was applied atdifferent depths in concrete.

FIG. 12 shows the crack formed when the blade of the apparatus of thepresent invention was allowed to penetrate to a depth of one andone-half (1.5) inches. Although the surface of the concrete in this testwas not subsequently smoothed very much, as evident by the marks left bythe roller, the crack formed was very prominent and substantial, as canbe seen.

FIG. 13 shows the crack formed when the blade of the apparatus of thepresent invention was allowed to penetrate to a depth of one (1) inch.Although the crack formed from this test is less prominent than thatdisplayed in FIG. 12, FIG. 13 shows that desirable results can beobtained with the present invention when the chemical is applied to adepth of one inch in a six inch thick slab of concrete.

FIG. 14 shows the crack formed when the blade of the apparatus of thepresent invention was allowed to penetrate to a depth of one-half (0.5)of an inch. Although the crack displayed in this figure appears to bevery small, this test shows that cracks in a concrete slab having athickness of six inches can be produced when chemical is applied to adepth of only one-half of an inch.

FIG. 15 shows the entire test slab that was used for the tests of thisexample.

The preceding examples can be repeated with similar success bysubstituting any of the generically or specifically described reactantsand/or operating conditions of this invention for those used in thepreceding examples.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverin the appended claims all such modifications and equivalents. Theentire disclosures of all references, applications, patents, andpublications cited above and/or in the attachments, and of thecorresponding application(s), are hereby incorporated by reference.

1. A method for creating a pre-stressed zone in concrete comprising:physically penetrating a top surface of wet concrete; applying achemical which retards or inhibits the setting of wet concrete at thephysical penetration; retarding or inhibiting the setting of the wetconcrete; and thereafter setting the wet concrete.
 2. The method ofclaim 1 wherein penetrating comprises rolling a substantially circularblade at least partially through a portion of the wet concrete.
 3. Themethod of claim 1 wherein penetrating comprises pressing a blade atleast partially into a portion of the wet concrete.
 4. The method ofclaim 1 wherein applying a chemical comprises disposing the chemical ona blade and placing the blade at least partially into the wet concrete.5. The method of claim 1 wherein applying a chemical comprises placing achemical-saturated rope below the top surface of the wet concrete. 6.The method of claim 5 further comprising disposing the rope at leastpartially within the wet concrete.
 7. The method of claim 6 whereindisposing the rope at least partially within the wet concrete comprisesdisposing the rope at least partially around a circumference of asubstantially circular rotatable blade.
 8. The method of claim 1 whereinapplying a chemical comprises inserting the chemical into an opening inthe wet concrete created by a blade.
 9. The method of claim 1 whereinapplying a chemical comprises applying the chemical below the topsurface of the wet concrete.
 10. The method of claim 1 furthercomprising smoothing the wet concrete.
 11. The method of claim 1 whereinthe chemical comprises an organic solvent.
 12. The method of claim 1wherein the chemical comprises aromatic
 100. 13. The method of claim 1wherein the chemical comprises mineral spirits.
 14. The method of claim1 wherein the chemical comprises a sugar-water solution.
 15. A methodfor creating a pre-stressed zone in concrete comprising: applying achemical which retards or inhibits the setting of wet concrete to onlythat portion of the concrete, when wet, wherein a crack is desired;retarding or inhibiting the setting of wet concrete where the crack isdesired; and allowing the concrete to set.
 16. The method of claim 15wherein the chemical comprises a sugar-water solution.
 17. The method ofclaim 15 wherein the chemical comprises an organic solvent.
 18. Themethod of claim 15 wherein the chemical comprises aromatic
 100. 19. Themethod of claim 15 wherein the chemical comprises mineral spirits. 20.The method of claim 15 wherein the chemical comprises mineral spirits.21. The method of claim 15 wherein the chemical is applied to a surfaceof only that portion of a wet concrete wherein a crack is desired. 22.The method of claim 15 wherein the chemical is applied in asubstantially straight line.
 23. The method of claim 15 wherein chemicalis disposed at least partially beneath a surface of only that portion ofa wet concrete wherein a crack is desired.